Torque measurement system for valve actuators

ABSTRACT

Disclosed is a valve actuator configured to determine, during operation of a valve by an alternating current (AC) motor of the valve actuator, an amount of torque produced by the AC motor. A process for measuring the amount of torque produced by the AC motor includes actuating a valve using the AC motor of the valve actuator, measuring, by a microcontroller of the valve actuator and during the actuating of the valve, a time interval between: (i) a first zero crossing of a waveform of AC voltage applied to the AC motor, and (ii) a second zero crossing of a waveform of AC current drawn by the AC motor, and determining, based on the time interval, an amount of torque produced by the AC motor during the actuating.

BACKGROUND

Valve actuators are configured to operate valves that regulate orcontrol the flow of a fluid through a passageway by opening, closing, orpartially obstructing the passageway. A number of forces and pressuresmay act on the valve from the fluid in the passageway, and, depending onthe environment in which a valve system is implemented, the amount oftorque required to actuate the valve may be significant. In someenvironments, such as valves that are implemented in a seawater system(e.g., a marine vessel), a valve may get stuck when the valve isinfrequently operated. For example, barnacles and other obstructions mayform over time, which may affect how much torque is required to actuatethe valve when it is necessary to do so. Thus, in many instances, it isuseful to measure and monitor the torque applied to the valve at anygiven time during operation of the valve.

Automated valve actuators typically include an electric motor. Somevalve actuators may include an electric motor in the form of a directcurrent (DC) motor(s). For DC motors, measuring torque is relativelysimple. Since the current that is drawn by the DC motor may be taken asan indirect measurement of the torque being produced by the DC motor, ameasurement of the current drawn by the DC motor may be used to derivethe torque, and such a measurement is relatively easy to make.

However, many valve actuators, such as those that are implemented inmarine environments like ocean liners and military ships, use one ormore alternating current (AC) motors as the drive mechanism foroperating the associated valve. For AC motors, one cannot simply measurethe current drawn by the AC motor. For instance, as the torque appliedby the AC motor increases, the absolute value of the AC current may notchange significantly, possibly making it difficult to derive torque froma simple measurement of AC current.

To this end, various systems have been developed to measure torqueapplied to a valve by an AC motor. Some systems involve the use ofmechanical-based sensors (e.g., strain gauges, brackets, etc.) thatmeasure the torque applied to the valve based on output of themechanical sensors. However, adding multiple mechanical-based sensors toa valve actuator can undesirably increase the weight and cost of theactuator. Electrical sensors have been developed to monitor torqueproduced by AC motors. However, conventional electrical sensors can becomplex in design, making for a system that is relatively difficult andcostly to manufacture.

SUMMARY

Described herein are techniques and systems for determining an amount oftorque produced by an alternating current (AC) motor used to operate avalve. The torque may be determined by measuring a time interval relatedto a phase shift between the waveform of the AC voltage applied to theAC motor and the waveform of the AC current drawn by the AC motor. Thephase shift between the waveform of the AC voltage applied to the ACmotor and the waveform of the AC current drawn by the AC motor can becorrelated to the amount of torque produced by the AC motor of the valveactuator. Thus, various techniques and systems disclosed herein leveragea measurement of a time interval between the first zero crossing of thewaveform of AC voltage applied to the AC motor and a second zerocrossing of the waveform of AC current drawn by the AC motor. The timeinterval measurement may be used as an indicator of the phase shiftbetween the two AC waveforms. Therefore, the measured time interval canbe utilized to derive the amount of torque produced by the AC motor ofthe valve actuator.

In some embodiments, a process for measuring the amount of torqueproduced by the AC motor includes actuating a valve using the AC motorof the valve actuator, and measuring, using a microcontroller of thevalve actuator and during the actuating of the valve, a time intervalbetween: (i) a first zero crossing of a waveform of AC voltage appliedto the AC motor, and (ii) a second zero crossing of a waveform of ACcurrent drawn by the AC motor, and determining, based on the timeinterval, an amount of torque produced by the AC motor during theactuating. The determined amount of torque may be used to verify thatthe valve is in a closed position.

Also disclosed herein is a valve actuator configured to determine thetorque applied to a valve that is coupled to the valve actuator. Thevalve actuator may include an AC motor to operate the valve, amicrocontroller to measure, during operation of the valve, a timeinterval between: (i) a first zero crossing of a waveform of AC voltageapplied to the AC motor, and (ii) a second zero crossing of a waveformof AC current drawn by the AC motor, and a torque measurement componentto determine, based on the time interval, an amount of torque producedby the AC motor during the operation of the valve. The torquemeasurement component may use the determined amount of torque to verifythat the valve is in a closed position.

Some examples of downstream uses of the measured torque are alsodescribed herein. Some of the downstream uses can help to rundiagnostics, prevent damage to components of the valve system,facilitate preventative maintenance for the components of the valvesystem, and allow the valve system to operate properly withinspecifications. The techniques and systems disclosed herein also improvethe technological process of closing a valve in order to increase thesafety for operators and other personnel in the field. For example,accurate torque measurements can be used to verify that the valve is ina fully closed position where the valve member is fully seated withinthe valve seat. Confirmation of a fluid-tight seal at the valve canprevent potentially hazardous situations from arising. Moreover, thevalve actuator of the various embodiments disclosed herein uses a timerembedded in the microcontroller of the valve actuator to digitallydetermine the amount of torque produced by the AC motor. Accordingly,various examples of a valve actuator disclosed herein can be lesscomplex in design and cheaper to manufacture than previous systemsdesigned to measure torque (e.g., systems with a plurality of straingauges and extra mechanical and electrical components).

This Summary is provided to introduce a selection of concepts in asimplified form that is further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is set forth with reference to the accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. Theuse of the same reference numbers in different figures indicates similaror identical items.

FIG. 1A illustrates a side elevation, and partial cross-sectional, viewof an example valve system including a valve actuator coupled to avalve, the valve being in a closed position.

FIG. 1B illustrates a side elevation, and partial cross-sectional, viewof an example valve system including a valve actuator coupled to avalve, the valve being in an opened position.

FIG. 2 illustrates a block diagram of an example valve actuator coupleda power source and a valve.

FIG. 3 is a graph of a waveform of AC voltage applied to the AC motorand a waveform of AC current drawn by the AC motor associated with apower source that provides power to a valve actuator, the graphillustrating torque measurement techniques according to variousembodiments.

FIG. 4 illustrates a flowchart of an example calibration process forestablishing torque calibration values and time intervals that can belater used for real-time torque measurement.

FIG. 5 illustrates a flowchart of an example process of determining,based on a measured time interval, an amount of torque produced by an ACmotor of a valve actuator.

FIG. 6 illustrates a flowchart of an example process of determiningwhether to stop or continue actuation of a valve based on measuredtorque produced by an AC motor of a valve actuator.

FIG. 7 illustrates a flowchart of an example process of determiningwhether to generate a preventative maintenance report based on measuredtorque produced by an AC motor of a valve actuator.

DETAILED DESCRIPTION

Described herein are techniques and systems for determining, duringoperation of a valve by an alternating current (AC) motor of a valveactuator, an amount of torque produced by the AC motor. The embodimentsdisclosed herein are described, by way of example and not limitation,with reference to a valve system that is suitable for use in marineenvironments, such as on ocean liners, or ships, including militaryships and submarines. However, it is to be appreciated that other typesof valve systems of varying designs may benefit from the techniques andsystems disclosed herein. Furthermore, the exemplary valve systemdescribed herein can be implemented within any suitable environment.

As used herein, the term “valve” is broadly construed to include, but isnot limited to, a device capable of regulating a flow of one or moresubstances through one or more passageways by opening, closing, orpartially blocking the one or more passageways. For example, a valve canhalt or control the flow of a fluid (e.g., a liquid, a gas, a fluidizedsolid, or mixtures thereof) through a conduit, such as a pipe, a tube, aline, a duct, or another structural component (e.g., a fitting) forconveying substances. Valve types include, without limitation, ballvalves, butterfly valves (e.g., concentric, double offset, tripleoffset, etc.), globe valves, plug valves, and the like.

Example Valve System

FIGS. 1A and 1B illustrate side elevation, and partial cross-sectional,views of an example valve system 100. The valve system 100 may beassociated with a larger system, such as a plant (e.g., a watertreatment plant, a power plant, etc.), a refinery, a factory, or avehicle, such as a watercraft. Furthermore, the valve system 100 mayrepresent one of a plurality of valve systems associated with the largersystem. As noted above, the valve system 100 may be implemented in anysuitable environment, which may include, without limitation, anon-corrosive environment, a corrosive environment, a magneticenvironment, a non-magnetic environment, a moist environment, a marineenvironment, or combinations thereof. In some embodiments, the valvesystem 100 may be used in civilian or military watercraft (e.g., oceanliners, floating vessels, boats, ships, submersible vehicles such assubmarines, and the like). Marine environments are known to beespecially harsh on the materials and the operation of theelectrical/mechanical components because of the abundance of moistureand corrosive substances, such as salt water. Such harsh environmentsmay greatly influence the amount of torque required to operate the valvesystem 100.

The valve system 100 includes a valve actuator 102 coupled to a valve104. The valve actuator 102 may comprise an assembly of varioussubcomponents. FIG. 1A illustrates the valve 104 in a closed position.FIG. 1B illustrates the valve 104 in an opened position. The valve 104may be positioned in a passageway 106 (See FIG. 1B; not shown in FIG.1A) and may operate between the opened and closed positions to regulatethe flow of fluids and like substances through the passageway 106. Thevalve actuator 102 may utilize various components to automaticallycontrol the operation/actuation of the valve 104 in order to open andclose the valve 104.

The valve actuator 102 may further include a main body 110 coupled to anelectric AC motor 112 (e.g., an AC induction motor). The main body 110may house internal components (e.g., mechanical and electricalcomponents, such as a gear train, microcontrollers, sensors, and so on).A housing of the main body 110 may protect the internal components fromthe external environment. The AC motor 112 is configured to convertelectrical energy to mechanical force or motion, and may, for example,include a rotor that moves with respect to a stator to generate torque.When energized, the AC motor 112 powers the actuation of the valve 104by transmitting the output of the AC motor 112 to a drive assembly (notshown) inside the main body 110. The drive assembly may include, withoutlimitation, a gear train, worm gear assembly, spur gears, planetarygears, drive belts, drive shafts, drive chains, clutch plates, and soon, that are configured to work together to transmit the output of theAC motor 112 to a connector 114, and ultimately to the valve 104. Thatis, the drive assembly in the main body 110 is configured to transmitthe force produced by the AC motor 112 to the connector 114 that couplesthe valve actuator 102 to the valve 104. The connector 114 may rotateabout an axis to transmit the force to the valve 104. A power line 116delivers power from a power source to the AC motor 112 and otherelectrical components that are provided in the main body 110.

The valve 104 may comprise a valve housing 118, a valve seat 120 that iscarried by the valve housing 118, and a valve member 122 that ismovable, shown as a generally circular disk, between a closed (FIG. 1A)and an opened (FIG. 1B) position. The subject matter disclosed herein isnot limited to a disk valve, and may include other types of valves 104of different types and geometries including, for example, valves wherethe action of opening and closing the passageway requires moving a partin a linear fashion rather than rotating a part. For example, the valve104 may include, without limitation, a gate valve, a globe valve, oranother type of “rising stem” valve, which may be operated by driving athreaded nut or similar component that lifts or lowers a threaded shaftas the nut turns. In this scenario, torque is applied to the threadednut, which, in turn, moves the shaft for operating the valve 104. Whenin the closed position (FIG. 1A), the valve member 122 is configured tocreates a fluid tight seal at the interface between the valve member 122and the valve seat 120. The valve 104 is considered to be in the closedposition when the valve member 122 seats against the valve seat 120 toform a fluid tight seal in the passageway 106 on either side of thevalve 104.

FIG. 2 illustrates a block diagram of an example valve actuator 102 thatis coupled to a power source 200 and a valve, such as the valve 104 ofFIGS. 1A and 1B. In some embodiments, the power source 200 may comprisea three-phase (3-phase) voltage source that produces three waveformsthat are equal in magnitude, but out of phase to each other by 120degrees)(°. However, any single-phase, two-phase, or poly-phase powersource 200 may be utilized herein without changing the basiccharacteristics of the system. For a power source 200 that is a 3-phasevoltage power source, each of the three voltage waveforms may berepresented by a sinusoidal wave having a predetermined frequency andmagnitude that is substantially equal to the other two waveforms.

FIG. 2 shows the power from the power source 200 being provided to thevalve actuator 102. The provisioning of the power to the valve actuator102 was represented in FIGS. 1A and 1B by the power line 116. Inparticular, the power from the power source 200 may be provided to oneor more motor controllers 202, and ultimately provided to the AC motor112 of the valve actuator 102. When the power source 200 is a 3-phasepower source, the AC motor 112 may comprise a 3-phase load, such as a3-phase AC induction motor. In this manner, electrical power from thepower source 200 may be coupled to the AC motor 112 for energizing theAC motor 112 for use in actuating the valve 104.

The motor controller(s) 202 may be communicatively coupled to the ACmotor 112 and programmed to control the AC motor 112 by causing the ACmotor 112 to provide varying levels of output power for operating thevalve 104 at different levels of torque, and to power the drive assemblyin both forward and reverse directions. In some embodiments, the motorcontroller(s) 202 may be configured, through a calibration process, tooperate the AC motor 112 at varying speeds or outputs according todifferent operating states of the valve 104 that require differentamounts of torque. For instance, an amount of torque required to openthe valve 104 under normal conditions may be known to the motorcontroller(s) 202 such that, during the operating state of “opening” thevalve 104 from a closed position, the motor controller(s) 202 maycontrol the AC motor 112 to operate at a predetermined speed or outputthat will result in application of the predetermined torque. Otheroperating states of the valve 104 (e.g., closing, seating, rotatingbetween open and closed positions, etc.) may require differentrespective torques. Accordingly, the motor controller(s) 202 can beprogrammed with a complete torque profile for the associated valve 104in order to apply an appropriate amount of torque for a particularoperating state of the valve 104.

The motor controller(s) 202 may be programmed based on, but not limitedto, the configuration of the drive assembly of the valve actuator 102, apredetermined torque profile or multiple specified torques for actuatingthe valve 104, end of travel positions for the valve 104, and the like.Thus, position settings, force settings, travel limits, or anycombination thereof may be used to program or calibrate the motorcontroller(s) 202 for operating the AC motor 112. The motorcontroller(s) 202 may include, but is not limited to, one or morecentral processing units (CPUs), microprocessors, digital signalprocessors (DSPs), application-specific integrated circuits (ASICs), andso on, and may include on-board or embedded storage, such as volatilememory, non-volatile memory, read-only memory (ROM), random accessmemory (RAM), and the like.

The valve actuator 102 is configured to electronically determine theamount of torque produced by the AC motor 112. In some examples, thevalve actuator 102 may determine torque at any given time duringoperation of the valve 104. It is recognized that the AC motor 112 ispowered from the power source 200 by a substantially constant peakvoltage. It is also recognized that the current that is supplied by thepower source 200 to the valve actuator 102 can be represented by thephase shift between the voltage AC waveform and the current AC waveformfor any given phase of the power source 200, such as a particular phaseof a 3-phase power supply. In other words, the phase shift/differencebetween the waveform of AC voltage applied to the AC motor 112 and thewaveform of AC current drawn by the AC motor 112 for each phase of thepower source 200 may be dependent on the type or extent of the loadprovided by the AC motor 112. The current will lag the voltage to adegree that depends on the amount of torque applied to the valve 104. Itis to be appreciated that the relative phase shift between each pair oflines (i.e., between each of two phases of a 3-phase power supply) doesnot change in response to changing torque; the relative phase shiftbetween each pair of lines of the power source 200 will remain atsubstantially 120° phase shift. However, as the torque applied to thevalve 104 increases, the phase shift between the waveform of the ACvoltage applied to the AC motor 112 and the waveform of the AC currentdrawn by the AC motor 112 for a given phase will change proportionallyto the change in torque. Thus, the phase shift between the waveform ofthe AC voltage applied to the AC motor 112 and the waveform of the ACcurrent drawn by the AC motor 112 can be an indicator of the torqueproduced by the AC motor 112 and applied to the valve 104.

Referring briefly to FIG. 3, a graph 300 shows squared-up versions of awaveform of the AC voltage 302 applied to the AC motor 112 and awaveform of the AC current 304 drawn by the AC motor 112. The waveformof AC voltage 302 applied to the AC motor 112 and the waveform of ACcurrent 304 drawn by the AC motor 112 are associated with the powersource 200 that is coupled to the valve actuator 102. For example, theAC waveforms 302 and 304 may correspond to one of the three phases of a3-phase voltage power source 200. In particular, the graph 300 depicts aphase shift that exists between the waveform of AC voltage 302 appliedto the AC motor 112 and the waveform of AC current 304 drawn by the ACmotor 112; in this case, the waveform of AC current 304 drawn by the ACmotor 112 is lagging the waveform of AC voltage 302 applied to the ACmotor 112. The graph 300 also illustrates multiple “zero-crossing”points (or “zero crossings”) for each of the AC waveforms 302 and 304,such as a first zero crossing 306 of the waveform of AC voltage 302applied to the AC motor 112 and a second zero crossing 308 of thewaveform of AC current 304 drawn by the AC motor 112.

Returning to FIG. 2, the valve actuator 102 may include one or more ACvoltage zero crossing sensors 204 and one or more AC current zerocrossing sensors 206. The AC voltage zero crossing sensor(s) 204 may beconfigured to sense or detect a zero crossing point of at least onewaveform of AC voltage 302 applied to the AC motor 112, and, inresponse, generate a signal that is indicative of the detected zerocrossing point. For example, the AC voltage zero crossing sensor(s) 204may detect the first zero crossing 306 of the waveform of AC voltage 302applied to the AC motor 112, which may correspond to a particular phaseof a 3-phase voltage power source 200. In some embodiments, multiple ACvoltage zero crossing sensors 204 may each be used for a particularphase of a two-phase or poly-phase power source 200. For example, threesensors 204 may be provided in the valve actuator 102 such that there isone sensor 204 for each of the three phases of a power supply 200comprising a 3-phase voltage power supply.

Similarly, the one or more AC current zero crossing sensors 206 may beconfigured to sense or detect a zero crossing point of at least onewaveform of AC current 304 drawn by the AC motor 112, and, in response,generate a signal that is indicative of the detected zero crossingpoint. For example, the AC current zero crossing sensor(s) 206 maydetect the second zero crossing 308 of the waveform of AC current 304drawn by the AC motor 112, which may correspond to a particular phase ofa 3-phase voltage power source 200. In some embodiments, multiple ACcurrent zero crossing sensors 206 may each correspond to a respectivephase of a two-phase or poly-phase power source 200. For example, threesensors 206 may be provided in the valve actuator 102 such that there isone sensor 206 for each of the three phases of a 3-phase voltage powersupply 200. By using the AC voltage zero crossing sensor(s) 204 and theAC current zero crossing sensor(s) 206, the valve actuator 102 may beable to detect various consecutive zero crossing points and generatesignals that are sent to a microcontroller 208 to measure a timeinterval between the receipt of the sequential zero crossing points onthe graph 300, as will be described in more detail below.

In some embodiments, the valve actuator 102 may comprise a convertor 210and a convertor 212, each configured to convert sinusoidal AC waveformsinto square waveforms, such as the square waveform of AC voltage 302applied to the AC motor 112 and the square waveform of AC current 304drawn by the AC motor 112 shown in FIG. 3. For instance, the convertors210 and 212 may comprise an electronic circuit configured to converthigh voltage AC sinusoidal waveforms to low voltage square waves. Anysuitable technique for converting sinusoidal waveforms to squared-upversions of the waveform may be utilized herein. Using squared-upversions of the AC waveforms allows for straight forward identificationof the transition from one digital state to another so that theidentified transition can be used as an event for stopping and startinga timer, as will be described in more detail below. In other words, thezero crossing time of the square wave corresponds to the time of thetransition from one digital state to another, and the zero crossing timecan be directly monitored using square waveforms. In alternativeembodiments, the AC sinusoidal waveforms may be processed withoutconverting the waveforms to square waveforms. In this scenario, the zerocrossing point may be determined by comparing the AC value to zero, andif the AC value equals zero, an event may be generated for stopping andstarting the below-described timer.

In some embodiments, the convertors 210 and 212 may further comprise, atleast in part, analog-to-digital (A/D) converters (not shown) to convertanalog power input signals to digital power input signals for downstreamdigital signal processing. In other embodiments, the zero crossingsensors 204 and 206 may themselves be configured to convert analogsignals to digital signals through the use of A/D converters embedded inthe sensors 204 and 206.

The microcontroller 208 may receive signals from the zero crossingsensors 204 and 206 whenever a zero crossing point is detected in awaveform of AC voltage 302 applied to the AC motor 112 and a waveform ofAC current 304 drawn by the AC motor 112, respectively. The signals forthe zero crossing point detected for the waveform of AC voltage 302applied to the AC motor 112 may be received before the zero crossingpoint signal for the waveform of AC current 304 drawn by the AC motor112 is received in instances when the waveform of AC current 304 drawnby the AC motor 112 lags the waveform of AC voltage 302 applied to theAC motor 112. The time interval between the receipt of the first zerocrossing 306 signal of the waveform of AC voltage 302 applied to the ACmotor 112 and the second zero crossing 308 signal of the waveform of ACcurrent 304 drawn by the AC motor 112 is indicative of the phase shiftbetween the two AC waveforms 302 and 304, and hence is indicative of thetorque produced by the AC motor 112.

Thus, the microcontroller 208 may include programmable interrupts 214that interrupt the microcontroller 208 to start a timer 216 (e.g., starta clock, a counter, etc.) upon receipt of a signal from the AC voltagezero crossing sensor(s) 204 that indicates the occurrence of a firstzero crossing 306 of the waveform of AC voltage 302 applied to the ACmotor 112. The programmable interrupts 214 subsequently interrupt themicrocontroller 208 in order to stop the timer 216 (e.g., stop theclock, the counter, etc.) upon receipt of a signal from the AC currentzero crossing sensor(s) 206 that indicates the occurrence of the secondzero crossing 308 of the waveform of AC current 304 drawn by the ACmotor 112. In this manner, the microcontroller 208 is able to measurethe time interval (At shown in FIG. 3) between the first zero crossing306 of the waveform of AC voltage 302 applied to the AC motor 112 andthe second zero crossing 308 of the waveform of AC current 304 drawn bythe AC motor 112. In other words, the microcontroller 208 is configuredto measure the change in time from the time of the first zero crossing306 of AC voltage applied to the AC motor 112 and the second zerocrossing 308 of AC current drawn by the AC motor 112. In someembodiments, the microcontroller 208 may include, but is not limited to,one or more CPUs, microprocessors, DSPs, ASICs, and so on, and mayinclude on-board or embedded storage, such as volatile memory,non-volatile memory, ROM, RAM, and the like.

The time interval, Δt, measured by the microcontroller 208 may then besent to a torque measurement component 218 stored in computer-readablememory 220 of the valve actuator 102. Computer-readable media mayinclude two types of computer-readable media, namely computer storagemedia and communication media. The memory 220 is an example of computerstorage media. Computer storage media may include volatile andnon-volatile, removable, and non-removable media implemented in anymethod or technology for storage of information, such as computerreadable instructions, data structures, program modules, or other data.Computer storage media includes, but is not limited to, RAM, ROM,erasable programmable read-only memory (EEPROM), flash memory or othermemory technology, compact disc read-only memory (CD-ROM), DVD, or otheroptical storage, magnetic cassettes, magnetic tape, magnetic diskstorage or other magnetic storage devices, or any other non-transmissionmedium that may be used to store the desired information and which maybe accessed by the valve actuator 102. Any such computer storage mediamay be part of the valve actuator 102. In general, computer storagemedia may include computer-executable instructions that, when executedby the microcontroller 208, perform various functions and/or operationsdescribed herein.

In contrast, communication media embody computer-readable instructions,data structures, program modules, or other data in a modulated datasignal, such as a carrier wave, or other transmission mechanism. Asdefined herein, computer storage media does not include communicationmedia.

The torque measurement component 218 may be configured to determine,based on the time interval Δt received from the microcontroller 208, atorque produced by the AC motor 112 and applied to the valve 104 duringoperation of the valve actuator 102. This determination of the torquemay involve converting the time interval Δt into a torque value havingconventional units, such as Newton-meters (N-m), foot-pounds (ft-lbs),inch-pounds (in-lbs), or the like. In some embodiments, a calibrationprocess may be performed in advance of the real-time torque measurementin order to obtain reference calibration points. An example calibrationprocess will be described in more detail below with reference to FIG. 4.With the availability of reference calibration points (e.g., referencetorque values and time intervals) obtained through a calibrationprocess, the torque measurement component 218 may interpolate the torquefrom a measured time interval Δt using the reference calibration points.

In some embodiments, the memory 220 of the valve actuator 102 includes adata store 221 containing torque limits 222 with corresponding operatingstates 224 of the valve 104. For example, a particular torque limit 222may be predefined for an “opening” operating state 224 to specify thetorque limit 222 for that operating state. The valve actuator 102 may beconfigured to apply a torque to the valve 104 that does not exceed theassociated torque limit 222 while opening the valve 104, so as toprevent damage to components of the valve system 100. The torque limit222 may be determined by carrying out a calibration procedure or thelike that monitors the torque applied to the valve 104 during variousoperating states of the valve 104. The torque limits 222 may be defineddifferently for different operating states. For example, a first torquelimit 222 may be associated with an “opening” operating state, and asecond, different torque limit 222 may be associated with a “closing”operating state, a “seating” operating state, and so on. In this manner,a complete torque profile for the valve 104 may be maintained by thevalve actuator 102 that can be used to compare measured torque to thetorque limits 222 for the various operating states of the valve 104.

In some embodiments, the torque measurement component 218 includes acomparator 226 that is configured to compare one or more torquemeasurements to a predetermined torque limit 222 for the operating statein question. Accordingly, the comparator 226 may determine a currentoperating state of the valve 104 that is associated with the measuredtime interval, Δt, such that the comparator 226 may “look-up” theoperating state 224 and the associated torque limit 222 to make thecomparison between the measured torque and the torque limit 222. Thiscomparison of measured torque to torque limits 222 may allow the valveactuator 102 to decide whether to continue or halt/stop the operation ofthe valve actuator 102. FIG. 2 shows a feedback loop 227 from the torquemeasurement component 218 to the motor controller(s) 202 for thispurpose. That is, the motor controller(s) 202 may receive a signal orother indication from the torque measurement component 218 that thecurrent torque meets or exceeds the torque limit 222 specified in thememory 220, and in response, the motor controller(s) 202 may stop the ACmotor 112 and halt any further actuation of the valve 104 in order tomitigate any possible damage to the valve 104 that may result fromapplying torque to the valve 104 at a level that exceeds the specifiedtorque limit 222. This scenario may occur when an obstruction inhibitsnormal operation of the valve 104, causing torque to exceed thespecified torque limits 222.

In some embodiments, the torque measurement component 218 may include analarm and reporting module 228 that is configured to send variousalerts, alarms, notifications, and/or reports to one or more othercomputing devices 230, such as over a network (e.g., the Internet, anintranet, a wired or wireless network, a cellular network, or acombinations thereof), or other type of connection (e.g., peer-to-peer(P2P), direct wireless or wired device-to-device connection, etc.), andso on.

The various communications that may be sent by the alarm and reportingmodule 228 may be triggered by one or more results of the comparator226. For instance, if the torque measured by the torque measurementcomponent 218 meets or exceeds a specified torque limit 222 for a givenoperating state 224, the alarm and reporting module 228 may, in responseto such an indication, trigger or transmit an alarm that is sent to theother computing device(s) 230. The alarm may cause a notification to beprovided at the other computing device(s) 230 including, withoutlimitation, an audible sound, a light (e.g., a flashing light emittingdiode (LED)), a short message service (SMS) text message, an electronicmail (e-mail), a banner notification, toast notification, or any similarnotification at the other computing device(s) 230. In this manner, auser of the other computing device(s) 230, such as a maintenanceoperator of the valve system 100, may receive the notification and maytake appropriate remedial action in response, such as dispatchingpersonnel to the valve system 100 to diagnose the problem, sending aticket to a valve maintenance entity, or sounding an alarm in the largersystem where the valve system 100 is implemented. For example, if properoperation of the valve 104 is needed to ensure safety to personnelaboard a vessel, an alarm on the vessel may be sounded in response tothe notification sent by the alarm and reporting module 228.

In some embodiments, a number of torque measurements may be made by thetorque measurement component 218 at multiple different times (e.g.,periodically, at regular or irregular intervals, etc.) for a particularoperating state 224. For example, a torque measurement can be made everytime the valve 104 is opened. These repeated torque measurements may beindividually compared to a predetermined torque limit 222 for purposesof ascertaining whether preventative maintenance is needed on acomponent of the valve system 100. For instance, if a certain number ofthe last N torque measurements exceeded the specified torque limit 222for a given operating state 224 (e.g., 5 of the last 10 torquemeasurements met or exceeded the torque limit 222), this may be anindication that a component (e.g., the valve seat 120, valve seals,packing, etc.) of the valve system 100 is experiencing wear ordeterioration and needs to be replaced in order to extend the operatinglife of the valve system 100. Accordingly, the alarm and reportingmodule 228 may be configured to generate and send a report detailingthat a valve component may be deteriorating and may be in need ofreplacement or maintenance. Such a report may be sent to the othercomputing device(s) 230, such as email accounts of relevant maintenancepersonnel for the valve system 100.

In another illustrative example, the valve seat 120 may wear over timesuch that the position for seating the valve member 122 has changed fromthe original calibrated position for seating the valve member 122 to adifferent position for seating the valve member 122. In this scenario, amaintenance operator may evaluate the position of the valve member 122during a “seating” operation and determine that the torque applied tothe valve during the “seating” operation is failing to completely seatthe valve member 122 (e.g., the valve member 122 stops short of fullseating position). The maintenance operator may decide to re-program themotor controller(s) 202 to apply a higher torque during the “seating”operation, causing the valve member 122 to seat properly within thevalve seat 120. Thus, the torque that is measured by the torquemeasurement component 218 can facilitate such a modification byproviding reference torque measurements.

Depending on the complexity of the valve 104 the operating states of thevalve 104 can have relatively complex torque profiles that requireapplication of precise amounts of torque at particular times orpositions of the valve member 122. For example, a triple offset valvemay have a relatively complex torque profile for a “seating” operationcompared to the relatively less complex concentric butterfly valve. Whenthe valve members 122 of a triple offset valve are seated to the valveseat 120 during a “seating” operation, the torque may initiallyincrease, followed by a decrease in the amount torque as the valvemember 122 rotates and/or moves into position, followed by anotherincrease in the amount of torque as the valve member 122 goes through afinal cranking motion to seat the valve member 122. If the right amountsof torque are not applied at precise times and/or positions of the valvemember 122, the valve member 122 may not seat properly during the“seating” operation, which may cause the valve member 122 to stop shortof a complete closing position, undershooting the final position.Monitoring torque using the valve actuator 102 of the embodimentsdisclosed herein can facilitate application of proper torque to thevalve 104 to ensure that valve operations are completed properly (e.g.,to verify that the valve member 122 is fully seated within the valveseat 120, indicating that the valve 104 is in the closed position),which can ensure safety of personnel in the field in certainimplementations.

Referring again to FIG. 3, the graph 300 shows squared-up versions of awaveform of AC voltage 302 applied to the AC motor 112 and a waveform ofAC current 304 drawn by the AC motor 112 to illustrate torquemeasurement techniques according to various embodiments. As describedabove, a suitable technique for determining the amount of torqueproduced by the AC motor 112 is by measuring, via the microcontroller208, the time interval, Δt, between the first zero crossing 306 of thewaveform of AC voltage 302 applied to the AC motor 112 and the secondzero crossing 308 of the waveform of AC current 304 drawn by the ACmotor 112, which is out-of-phase with the waveform of AC voltage 302applied to the AC motor 112 (e.g., lagging the waveform of AC voltage302 applied to the AC motor 112). In some embodiments, measurement ofthe time interval, Δt, is accomplished by interrupting themicrocontroller 208 upon receipt of the first zero crossing 306 signalfrom the AC voltage zero crossing sensor(s) 204 in order to start thetimer 216, and interrupting the microcontroller 208 upon receipt of thesecond zero crossing 308 signal from the AC current zero crossingsensor(s) 206 in order to stop the timer 216. The resulting timeinterval, Δt, measured by the timer 216 is indicative of the phase shiftbetween the two AC waveforms 302 and 304, and hence is indicative of thetorque produced by the AC motor 112. Accordingly, the measured timeinterval, Δt, may be sent to the torque measurement component 218 todetermine, based on the time interval, Δt, a torque produced by the ACmotor 112 and applied to the valve 104 during operation of the valveactuator 102.

Another technique for determining torque produced by the AC motor 112 isillustrated in FIG. 3. Particularly, FIG. 3 shows a voltage signal 310that can be created by an electronic circuit (e.g., an analog circuit).The voltage signal 310 ramps during the time interval, Δt, shown in FIG.3. In other words, this artificial voltage signal 310 can be created byan electronic circuit (not shown) in the valve actuator 102, the voltagesignal 310 starting at zero voltage, and, upon the first zero crossingpoint 306 of the waveform of AC voltage 302 applied to the AC motor 112,the electronic circuit starts a steady increase in voltage at apredetermined rate. The electronic circuit may continue to increase thevoltage, as shown by the ramping portion of the voltage signal 310,until the point where the waveform of AC current 304 drawn by the ACmotor 112 crosses the voltage signal 310 (which coincides with thesecond zero crossing 308 in FIG. 3), and this point is designated as themeasurement point 312 in FIG. 3. The voltage level at the measurementpoint 312 corresponds to the torque produced by the AC motor 112. Thecreation of the artificial voltage signal 310 solely for purposes ofmeasuring the voltage to derive torque is expected to cost more than themeasurement of the time interval, Δt, using the microcontroller 208 withthe embedded timer 216. The voltage technique also uses an additionalelectronic circuit for creating the artificial voltage signal 310.Nevertheless, the voltage method can be a suitable alternate techniquein some implementations.

Example Processes

The processes described in this disclosure may be implemented by thearchitectures described herein, or by other architectures. Theseprocesses are illustrated as a collection of blocks in a logical flowgraph. Some of the blocks represent operations that can be implementedin hardware, software, or a combination thereof. In the context ofsoftware, the blocks represent computer-executable instructions storedon one or more computer-readable storage media that, when executed byone or more processors, perform the recited operations. Generally,computer-executable instructions include routines, programs, objects,components, data structures, and the like that perform particularfunctions or implement particular abstract data types. The order inwhich the operations are described is not intended to be construed as alimitation, and any number of the described blocks can be combined inany order or in parallel to implement the processes. It is understoodthat the following processes may be implemented on other architecturesas well.

FIG. 4 illustrates a flowchart of an example calibration process 400 forestablishing torque calibration values and time intervals that can belater used for real-time torque measurement. The calibration process 400may be implemented in a system including a valve actuator, such as thevalve actuator 102, mounted on a test stand that is configured tosimulate a valve, such as the valve 104. Any suitable rotating assembly(e.g., a truck disk brake or the like) may be utilized for the teststand to simulate the valve 104. The test stand may be situated so thatthe force required to rotate the test stand can be measured.Furthermore, the amount of torque required to operate the test stand maybe adjustable so that different time interval measurements may be takenfor different amounts of torque applied to the test stand. Moreover, thetorque may be measured in any suitable units, such as ft-lbs.

At 402, the valve actuator 102 may actuate the test stand with the loadof the test stand set to a first amount of torque, which may be a knownlow amount of torque. The known low torque amount may be chosen to be anamount of torque at the lower limits of the expected operating range oftorque values.

At 404, the time interval of the phase difference, such as the timeinterval, Δt, shown in FIG. 3, may be measured for the known low torquevalue. At 406, the measured time interval, Δt, may be stored (e.g., inthe data store 221) in association with the corresponding known lowtorque value. The stored time interval and torque value may bedesignated as reference calibration values or calibrated points.

At 408, the load of the test stand may be set to a second amount oftorque, which may be a known high amount of torque at the upper limitsof the expected operating range. At 410, the time interval of the phasedifference may be measured for the known high torque value, and at 412,the measured time interval Δt may be stored (e.g., in the data store221) in association with the corresponding known high torque value. Thestored time interval and torque value may be designated as another setof reference calibration values/points.

Although the calibration process 400 describes measuring a time intervalfor a known low torque value and then repeating the steps for a knownhigh torque value, the process 400 may measure the time interval for theknown high torque value before the measurement for the known low torquevalue. In some cases, there may be mechanical or electricalcharacteristics that differ when the AC motor 112 of the valve actuator102 and any associated gearing is operated in different directions(e.g., forward or reverse direction). Accordingly, in some embodiments,independent calibrations may be performed in each direction (e.g., valveopening direction and valve closing direction).

In cases where there is a non-linear relationship between the torque andthe phase difference between the waveform of AC voltage 302 applied tothe AC motor 112 and the waveform of AC current 304 drawn by the ACmotor 112, the calibration process 400 may involve determiningintermediate calibration points (i.e., calibration points in between thehigh and low calibration points). In some embodiments, an interpolationbetween a plurality of calibration points may be made. In otherembodiments, a curve fitting technique may be used with severalcalibration points along the expected operating range of torque values.The calibration process 400 may be carried out for individual valveactuators 102 and/or AC motors 112. Alternatively, a single calibrationprocess 400 may be performed on a representative valve actuator 102and/or AC motor 112 that can be leveraged for an inventory of valveactuators 102, assuming that the calibration characteristics aresubstantially consistent from one AC motor to another and/or from onevalve actuator to another.

FIG. 5 illustrates a flowchart of an example process 500 of determining,based on a measured time interval, an amount of torque produced by an ACmotor 112 of a valve actuator 102. The process 500 may be implemented byone or more components of the valve actuator 102, and in particular, theAC motor 112, the microcontroller 208, and the torque measurementcomponent 218.

At 502, the AC motor 112 may actuate the valve 104. The actuation of thevalve at 104 may represent valve actuation during any operating state ofthe valve, such as opening, closing, seating, and so on. In particular,the AC motor 112 output may be transferred to the valve 104 by applyingtorque to a connector 114 that causes the valve member 122 to move(e.g., rotate, translate, or combinations thereof).

At 504, the microcontroller 208 may measure a time interval, Δt, betweena first zero crossing 306 of a waveform of AC voltage 302 applied to theAC motor 112 and a second zero crossing 308 of a waveform of AC current304 drawn by the AC motor 112, the AC waveforms 302 and 304 beingassociated with a power source 200 coupled to the valve actuator 102. Insome embodiments, the power source 200 comprises a 3-phase power source,and the waveform of AC voltage 302 applied to the AC motor 112 and thewaveform of AC current 304 drawn by the AC motor 112 represent the ACwaveforms for one of the three phases of the 3-phase power source. Ininstances where the waveform of AC current 304 drawn by the AC motor 112lags behind the waveform of AC voltage 302 applied to the AC motor 112,the second zero crossing 308 may comprise the next, sequential zerocrossing after the first zero crossing 306 among multiple sequentialzero crossings on the graph 300 of FIG. 3. Since the phase shift betweenthe waveform of AC voltage 302 applied to the AC motor 112 and thewaveform of AC current 304 drawn by the AC motor 112 is indicative ofthe amount of torque produced by the AC motor 112, the time interval,Δt, will change with a change in the amount of torque produced by the ACmotor 112.

At 506, the torque measurement component 218 determines the amount oftorque produced by the AC motor 112 based on the time interval, Δt,measured at 504. This determination of the amount of torque at 506 mayinvolve converting the time interval, Δt, into a torque value havingconventional units, such as N-m, ft-lbs, in-lbs, or the like. In someembodiments, the torque measurement component 218 may reference orotherwise access calibration points that were obtained through thecalibration process 400 of FIG. 4, and the torque measurement component218 may interpolate the calibration points from the time interval, Δt,measured at 504 to derive the torque value at 506. When the phase shiftof the current for the AC motor 112 is linearly related to the torque, alinear interpolation along a line established by two sets of calibrationpoints (e.g., a high reference torque value and corresponding timeinterval and a low reference torque value and corresponding timeinterval) may be sufficient. In some embodiments, interpolation on acalibration curve may be performed when a non-linear relationship existsbetween the torque and the phase shift of the current for the AC motor112. The process steps 502-506 may iterate during operation of the valve104 at any suitable frequency, or upon initiation of a new operatingstate of the valve 104. In this manner, torque measurement may berepeatedly made for continuous monitoring of torque applied to the valve104 during various operating states of the valve.

At 508, an optional step of storing the torque measurement determined at506 may be performed. For example, the torque determined at 506 may bestored in the memory 220 of the valve actuator 102 along with otherhistorical torque measurements. The torque measurements may bemaintained in the memory 220 for a period of time and then aged out anddeleted, or sent to the other computing device(s) 230 for permanentstorage on a remote computing system with perhaps larger memorycapacity. In some embodiments, the torque measurements are stored at 508in association with an operating state of the valve 104 during which thetorque was determined. For example, if the actuation of the valve 104 atstep 502 involves opening the valve 104 as part of an “opening”operating state, the torque that is determined at 506 may be stored at508 in association with the “opening” operating state.

In some embodiments, the amount of torque that was determined at 506 maybe utilized for various downstream functions. For example, the amount oftorque may be used, by the torque measurement component 218, to verifythat the valve 104 is in the closed position where the valve member 122is fully seated within the valve seat 120. This confirmation may involvethe comparator 226 comparing the amount of torque determined at 506 to atorque limit 222 in the data store 221. In some cases, the referencedtorque limit 222 may be a lower limit that is to be met in order toensure proper closure of the valve 104. For example, if the amount oftorque determined at 506 is less than the referenced torque limit 222used to ensure full closure of the valve 104, this may indicate that thevalve member 122 was not fully seated within the valve seat 120 during aclosing operation of the valve 104, and remedial action may be taken inresponse to such an indication.

FIG. 6 illustrates a flowchart of an example process 600 of determiningwhether to stop or continue actuation of a valve 104 based on measuredtorque produced by an AC motor 112 of a valve actuator 102. The process600 may continue from step 508 of the process 500 of FIG. 5, as shown bythe off-page reference “A,” and the process 600 may be implemented byone or more components of the valve actuator 102, and in particular, thetorque measurement component 218 and the motor controller(s) 202.

At 602, the torque measurement component 218 may retrieve, for a currentoperating state 224 (e.g., opening, closing, seating, etc.) of the valve104, a torque limit 222 from memory 220 of the valve actuator 102. Thetorque limit 222 may have been specified as part of a calibrationprocess during initial setup of the valve system 100.

At 604, the comparator 226 of the valve actuator 102 may determinewhether the amount of torque determined at step 506 of the process 500meets or exceeds the torque limit 222 retrieved at 602. If the measuredtorque is less than the torque limit 222, the valve actuator 102 maycontinue operation of the valve 104 by following the off-page reference“C” back to the beginning of the process 500 so that other torquemeasurement can be made during operation of the valve 104 using theprocess 500.

If, on the other hand, the measured torque meets or exceeds the torquelimit 222 at decision block 604, the process 600 may proceed to 606where the actuation of the valve 104 is halted. For example, the motorcontroller 202 may receive an indication from the torque measurementcomponent 218 that the torque limit 222 has been met or exceeded, and,in response, the motor controller 202 may stop the operation of the ACmotor 112 to refrain from actuating the valve 104 any further. Haltingthe operation of the valve 104 in this manner may prevent damage tocomponents of the valve system 100 that can be caused by application ofexcessive torque to the valve 104 that is not needed for normaloperation of the valve 104.

In some embodiments, the process 600 may include an optional step 608 ofsounding an alarm in response to the determination at 604 that themeasured torque meets or exceeds the torque limit 222, and in additionto stopping the actuation of the valve 104 at step 606. For example, analarm may be issued by the alarm and reporting module 228 of the valveactuator 102 and sent to the other computing device(s) 230 so that anotification may be provided at the other computing device(s) 230 inorder to apprise users of the other computing device(s) 230 of thealarm. The users of the other computing device(s) 230 may choose to takeremedial action in response to receiving the alarm notification.

FIG. 7 illustrates a flowchart of an example process 700 of determiningwhether to generate a preventative maintenance report based on measuredtorque produced by an AC motor 112 of a valve actuator 102. The process700 may continue from step 508 of the process 500 of FIG. 5, as shown bythe off-page reference “A,” and the process 700 may be implemented byone or more components of the valve actuator 102, and in particular, thetorque measurement component 218 and the alarm and reporting module 228.

At 702, the torque measurement component 218 may retrieve, for a currentoperating state 224 (e.g., opening, closing, seating, etc.) of the valve104, multiple torque measurements from memory 220 of the valve actuator102. The multiple torque measurements may have been stored at step 508of the process 500 over time for various instances where a particularoperating state 224 was performed by the valve system 100. For example,over a period of time (e.g., the course of a week), the valve system 100may have opened the valve 104 a number of times, and the amount oftorque applied to the valve 104 during those individual openingoperations may have been measured and stored using the process 500, andthe multiple torque measurements may have been subsequently retrieved atstep 702.

At 704, the comparator 226 may compare each of the multiple torquemeasurements to a torque limit 222 to determine (e.g., count) how manyof the multiple torque measurements meet or exceed the retrieved torquelimit 222.

At 706, a determination is made as to whether the number of torquemeasurements determined to have met or exceeded the torque limit 222meets or exceeds a threshold number of measurements. For example, thethreshold number of measurements at 706 may be set at ten measurementssuch that the threshold is met or exceeded if there are ten or morehistorical torque measurements that exceed the torque limit 222 based onthe determination at 704. If the number of torque measurements that meetor exceed the torque limit 222 is below the threshold number ofmeasurements at 706, the process 700 may proceed, via the off-pagereference “C,” back to the beginning of the process 500 where theoperation of the valve 104 may continue so that more torque measurementsmay be taken.

If, on the other hand, there is at least a threshold number of torquemeasurements that exceed the threshold number of measurements at 706,the process 700 may proceed to 708 where the alarm and reporting module228 generates a report that a component of the valve system 100 may bein a deteriorating condition and in need of preventative maintenance(e.g., replacement, repair, etc.). The report may be sent to the othercomputing device(s) 230 so that users of the other computing device(s)230 may be informed of the deteriorating condition so that remedialsteps can be taken to maintain the valve system 100 for extendedoperation. Thus, the process 700 may facilitate preventative maintenancemeasures to extend the operating life of the valve system 100 throughmonitoring of torque applied to the valve 104 during operation of thevalve 104.

The environment and individual elements described herein may of courseinclude many other logical, programmatic, and physical components, ofwhich those shown in the accompanying figures are merely examples thatare related to the discussion herein.

Other architectures may be used to implement the describedfunctionality, and are intended to be within the scope of thisdisclosure. Furthermore, although specific distributions ofresponsibilities are defined above for purposes of discussion, thevarious functions and responsibilities might be distributed and dividedin different ways, depending on circumstances.

CONCLUSION

Although the application describes embodiments having specificstructural features and/or methodological acts, it is to be understoodthat the claims are not necessarily limited to the specific features oracts described. Rather, the specific features and acts are merelyillustrative some embodiments that fall within the scope of the claimsof the application.

What is claimed is:
 1. A valve actuator for actuating a valve, the valveactuator comprising: an alternating current (AC) motor to operate thevalve; a microcontroller to measure, during operation of the valve, atime interval between: (i) a first zero crossing of a waveform of ACvoltage applied to the AC motor, and (ii) a second zero crossing of awaveform of AC current drawn by the AC motor; and a torque measurementcomponent to: (i) determine, based on the time interval, an amount oftorque produced by the AC motor during the operation of the valve, and(ii) verify, based on the amount of the torque, that the valve is in aclosed position.
 2. The valve actuator of claim 1, further comprisingone or more AC voltage zero crossing sensors to detect the first zerocrossing of the waveform of the AC voltage applied to the AC motor andgenerate a first signal in response to detection of the first zerocrossing, wherein the microcontroller further comprises a timer thatstarts a clock upon receipt of the first signal at the microcontroller.3. The valve actuator of claim 2, further comprising one or more ACcurrent zero crossing sensors to detect the second zero crossing of thewaveform of the AC current drawn by the AC motor and generate a secondsignal in response to detection of the second zero crossing, wherein thetimer stops the clock upon receipt of the second signal, and wherein themicrocontroller is configured to measure the time interval as an amountof time that has accrued since starting the clock when the timer stopsthe clock.
 4. The valve actuator of claim 1, further comprising a motorcontroller that is configured to: continue operation of the AC motor tocontinue the operation of the valve if the amount of the torque is belowa predetermined torque limit; and stop the operation the AC motor tohalt the operation of the valve if the amount of the torque meets orexceeds the predetermined torque limit.
 5. The valve actuator of claim4, wherein the predetermined torque limit corresponds to an operatingstate of the valve among multiple possible operating states of thevalve.
 6. The valve actuator of claim 4, further comprising an alarm andreporting module to issue an alarm upon the amount of the torque meetingor exceeding the predetermined torque limit.
 7. The valve actuator ofclaim 1, wherein the torque measurement component is further configuredto: retrieve multiple torque measurements that have been made over timefor an operating state of the valve among multiple possible operatingstates of the valve; compare individual ones of the multiple torquemeasurements to a predetermined torque limit associated with theoperating state; count a number of the multiple torque measurements thatmeet or exceed the predetermined torque limit; and upon determining thatthe number of the multiple torque measurements meets or exceeds athreshold number of measurements, generate a report indicating that avalve component is in a deteriorating condition.
 8. A method forimplementation by a valve actuator, the method comprising: actuating avalve using an alternating current (AC) motor of the valve actuator;measuring, by a microcontroller and during the actuating of the valve, atime interval between: (i) a first zero crossing of a waveform of ACvoltage applied to the AC motor, and (ii) a second zero crossing of awaveform of AC current drawn by the AC motor; and determining, based onthe time interval, an amount of torque produced by the AC motor duringthe actuating.
 9. The method of claim 8, wherein the determining theamount of the torque comprises: referencing calibration points that wereobtained from calibrating the valve actuator; and interpolating thecalibration points from the time interval to derive the amount of thetorque.
 10. The method of claim 8, further comprising: detecting, by oneor more AC voltage zero crossing sensors, the first zero crossing of thewaveform of the AC voltage applied to the AC motor; generating, inresponse to the detecting of the first zero crossing, a first signal;and starting a timer of the microcontroller in response to receipt ofthe first signal at the microcontroller.
 11. The method of claim 10,further comprising: detecting, by one or more AC current zero crossingsensors, the second zero crossing of the waveform of the AC currentdrawn by the AC motor; generating, in response to the detecting of thesecond zero crossing, a second signal; and stopping the timer of themicrocontroller in response to receipt of the second signal at themicrocontroller, wherein the measuring the time interval comprisesmeasuring an amount of time that has accrued since the starting of thetimer when the timer is stopped.
 12. The method of claim 8, furthercomprising: continuing operation of the AC motor to continue theactuating of the valve if the amount of the torque is below apredetermined torque limit; or stopping the operation of the AC motor tohalt the actuating of the valve if the amount of the torque meets orexceeds the predetermined torque limit.
 13. The method of claim 12,wherein the predetermined torque limit corresponds to an operating stateof the valve among multiple possible operating states.
 14. The method ofclaim 12, further comprising issuing an alarm upon the amount of thetorque meeting or exceeding the predetermined torque limit.
 15. Themethod of claim 8, further comprising: retrieving multiple differenttorque measurements that have been made over time for an operating stateof the valve among multiple possible operating states of the valve;comparing individual ones of the multiple different torque measurementsto a predetermined torque limit associated with the operating state;counting a number of the multiple different torque measurements thatmeet or exceed the predetermined torque limit; and upon determining thatthe number of the multiple different torque measurements meets orexceeds a threshold number of measurements, generating a reportindicating that a valve component is in a deteriorating condition.
 16. Amethod for implementation by a valve actuator, the method comprising:energizing an alternating current (AC) motor of the valve actuator froma power supply electrically coupled to the valve actuator; operating theAC motor to cause actuation of a valve coupled to the valve actuator;determining, by a microcontroller and during the actuation of the valve,a time of a first zero crossing of a waveform of AC voltage applied tothe AC motor; determining, by the microcontroller and during theactuation of the valve, a time of a second zero crossing of a waveformof AC current drawn by the AC motor; measuring, by the microcontroller,a time interval from the time of the first zero crossing to the time ofthe second zero crossing; and determining, based on the time interval,an amount of torque produced by the AC motor during the actuation of thevalve.
 17. The method of claim 16, wherein the power supply comprises athree-phase power supply, and wherein the waveform of the AC voltageapplied to the AC motor and the waveform of the AC current drawn by theAC motor are associated with a particular phase of the three-phase powersupply.
 18. The method of claim 16, further comprising: interrupting themicrocontroller at the time of the first zero crossing to start a timerincluded in the microcontroller; interrupting the microcontroller at thetime of the second zero crossing to stop the timer; and wherein themeasuring the time interval comprises measuring an amount of time thathas accrued since the start of the timer when the timer is stopped. 19.The method of claim 16, further comprising: retrieving a predeterminedtorque limit corresponding to a current operating state of the valveamong multiple possible operating states of the valve; and continuingoperation of the AC motor to continue the actuation of the valve if theamount of the torque is below the predetermined torque limit; orstopping the operation of the AC motor to halt the actuation of thevalve if the amount of the torque meets or exceeds the predeterminedtorque limit.
 20. The method of claim 19, further comprising generatingan alarm upon the amount of the torque meeting or exceeding thepredetermined torque limit.